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 Yearling
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comment How to force Nmap to use -PE option on local network?
@hg8 Also notice use of -sP (an alias for -sn) to skip the port scan phase, only running host discovery (a.k.a. "ping"). All the TCP packets shown in your Wireshark capture are port scan packets, not host discovery.
Jan
25
comment bash multi-threads help require
This is counterproductive. Nmap's internal parallelism is much more efficient and easier to use: nmap -iL $filename -p $2 -oG - | awk '/\/open\//{print $2}' >> total.txt does the same thing but faster.
Jan
25
comment bash multi-threads help require
This is the correct answer. Nmap does not need to be multithreaded because it uses socket parallelism to scan many addresses at once. Launching 100 concurrent Nmap processes will almost certainly make your scan slower, because each will interfere with the others' timing checks and congestion avoidance.
Dec
31
answered Can nmap display only hosts with specific ports open?
Oct
13
comment nmap scan takes 50 minutes
@cfye14 It affects any Linux >3.2 and libpcap >1.5
Oct
13
comment nmap scan takes 50 minutes
@cfye14 -sn goes fast because it doesn't do a port scan, only host discovery. There's a small chance you're experiencing this bug, too: github.com/nmap/nmap/issues/34
Oct
11
answered nmap scan takes 50 minutes
Aug
25
comment mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled
Please clarify what you mean by "on windows." What DNS servers do you expect to be configured? Include diagnostic output regarding your DNS setup: cat /etc/resolv.conf
May
12
comment How many bytes occupy a simple nmap to a host?
Nmap itself can tell you how many bytes it sends for some scan types, when you use the -v flag: Raw packets sent: 1175 (51.676KB) | Rcvd: 1169 (46.776KB)
Mar
2
awarded  Yearling
Jan
29
answered Output only the IP addresses of the online machines with nmap
Jan
10
comment nmap -sn lists all active hosts on my network, but nmap -sL does not
Great answer. Your note about ICMP Echo Request packets is not quite right, though. Nmap uses lots of techniques to discover hosts, but ICMP Echo Request is hardly ever used on a local LAN. Instead Nmap uses simple ARP requests, which are a prerequisite to any IP communication on Ethernet-like links.
Dec
27
revised Nmap -sn: scan or no scan?
Notify of correction to official documentation.
Nov
12
comment Nmap script execution to detect heartbleed is failing
@user53029 I'd recommend removing the old one, as long as you have the required dependencies. I use checkinstall to make dpkg manage it and allow easy removal and upgrades. Just be sure to apt-get install libssl-dev before you build; all other build dependencies should be included (apart from a compiler, of course!).
Nov
12
awarded  Explainer
Nov
11
revised Nmap script execution to detect heartbleed is failing
Fix copy-paste-truncated link
Nov
11
suggested approved edit on Nmap script execution to detect heartbleed is failing
Nov
11
answered Nmap script execution to detect heartbleed is failing
Oct
20
answered Can masscan use the Nmap Scripting Engine?
Sep
12
comment nmap ipv6 os scan fails
@SebastianBrestin The current version of Nmap is 6.47. IPv4 and IPv6 use completely different fingerprinting engines with separate databases, but the recommendations still apply.